I have both units and while the XS35 editing features are superior, I'll echo what others have said, which is "Only if the burner is in good working condition". These burners are proprietary, you can't just replace them with a typical ATA DVD burner.
The burner in mine barely works and wastes a lot of disks. This is the main reason I bought the RDRHX780 and when I eventually copy everything off the XS35, I'll probably sell it if I can find a buyer. I paid $270 for my RDRHX780 at BB (open box). The burner on the Sony opens very smoothly, unlike the clunk that the XS35 drive opens and closes with. It's very quite while burning disks, works well with cheap disks and doesn't fail burning with any of them. I can't say the XS35 burner was like that even when it was new. Also reads burned dual-layer disk with no problem. The Toshiba can't read them at all.
The fan of the RDRHX780 turns off when you switch off the unit. Although I have modified the fan of the XS35 so it almost can't be heard, it's still too loud for a room I'm sleeping in.
I don't really understand why everyone cares so much about DVD-RAM when you have a hard drive. I personally like the ability of the RDRHX780 to burn dual-layer disks and it not only upscales DVD video, but any video source that comes in to it via s-video. If you use the HDMI output, you can upscale to 1080p as well. Looks great, and improves the picture quality of my standard def satellite. Recordings from both units look fantastic. There's no appreciable difference, other than the upscaling from the RDRHX780.
I've had no problem with copy protection from any source so far on either unit and I'm not using hacked satellite, it's legit ExpressVu. One of the features I especially like is that it will pick up the name of the show when it's encoded in the signal. Works through s-video input too, you don't have to have coax connected. It also allows me to name my timers, and that's very nice, because even if it doesn't have the show name encoded in the signal, I still see the show name in my list of recordings. Unlike the manual timers of XS35's lousy TVGuide OnScreen that has nothing but date to identify your shows with and doesn't have a skip once feature. Manual timers are the only way for most, if not all satellite users with aftermarket DVRs. Best of all, you plug a standard USB keyboard into the port in the front of the Sony, and you can quickly edit show names. This is a major plus for me personally, I hate entering title and other info with a remote. The Sony also has quick timers like they used to have on their VCRs (a very convenient feature).
The only significant downside to the RDRHX780 is that it does not have Pause LiveTV or Timeslip mode, per-say, but there's still a simple way to do this manually and automatically. If you start recording and then press play , it's essentially the same thing. The Sony enters into Chase Play mode. You can then pause, stop, ff and rw without effecting the recording. You just have to manually delete it when your done if you don't want to keep it. There's no prompt to ask you if you want to save or delete the timeslip content like the XS35 does. You can easily automate this action to one button with a programmable learning remote. You don't have to spend a lot on a universal remote to do this either. I have 2 of the OFA URC8920 eight unit remotes and they work perfect for any device I own. Even my AppleTV. I paid $35 for each of them.
Couple of other nice features of the Sony are the auto chapter markers by time and/or scene change. This is somewhat of a pain, and somewhat helpful because it makes it easier to edit out commercials, but it's not Tivo, so it can sometimes add too many chapter makers. Good thing is that removing them is very easy. The Sony also allows you to view a recording already in progress from the beginning by simply pressing the play button. The XS35 requires that you first press Timeslip and then the chapter back button. Not very intuitive. Sony has a dedicated "stop recording" button, so the recordings can't get easily screwed up by accidentally pressing the stop button. That simply stops Chase Play if it's active and you can start right back in the same spot by pressing play again. I programmed my universal remote so that when I hold down the PVR button for 2 second, it performs the "stop recording" function.
I really do think the editing functions on the X35 are far superior to the Sony, but it's been easy to live without most of them. I'm really more pleased with the convenience features of the Sony. Personally, I'd buy a new Sony RDRHX780 with a warranty, rather then investing $150 into an XS35 with no warranty.